Potential Impacts of Climate Change
post by JonahS (JonahSinick) · 2013-05-22T07:22:20.482Z · LW · GW · Legacy · 44 commentsContents
Potential Impacts according to the IPCC Overly weak assumptions regarding adaptation? The IPCC as overly optimistic? Tail risk None 44 comments
According to a recent press release from UC Berkeley’s School of Law:
Overheated: The Human Cost of Climate Change predicts a grim future for billions of people in this century. It is a factual account of a staggering toll, based on hard data […] “Climate change is the most important problem facing the international community in the 21st century,” Guzman said.
Guzman's view is shared by many.
While I have not read Guzman’s book, I have read GiveWell’s summary of the IPCC, as well as notes on GiveWell’s conversations with climate change experts. Based on these, I’ve come to the tentative conclusion that while climate change is an important issue, it’s unlikely to be the most important issue, though there is uncertainty, owing to poorly understood tail risk.
Potential Impacts according to the IPCC
GiveWell recently wrote up a summary and review of some of the impacts of unmitigated climate change, as described by the Intergovernmental Panel on Climate Change's 2007 Fourth Assessment Report. GiveWell writes:
The report suggests that unmitigated climate change would have extraordinarily negative humanitarian impacts across all of the outcomes we looked at: hunger, water stress, flooding, extreme weather, health, biodiversity, and the economy. Successfully mitigating these negative impacts would carry vast humanitarian benefits.
When looking at the range of possible futures outlined in the report, the bulk of the variation (in humanitarian terms) comes from variation in the level of assumed economic growth and adaptation, rather than variation in the amount of climate change. Of the outcomes we examined, only biodiversity is expected to be unambiguously worse off in the future as a result of both climate change and economic growth.
The most succinct summary of the expected impact is given by a GDP drop estimate:
Most recently, Stern (2007) took account of a full range of both impacts and possible outcomes. […] Using equity weights to reflect the expectation that a disproportionate share of the climate-change burden will fall on poor regions of the world increased their estimated reduction in equivalent consumption per head to 20%.
Such a drop would be highly undesirable, but far from catastrophic. World GDP has been growing at a rate of ~3%, so this corresponds only to a set-back of ~6 years. Poor countries are expected to become richer regardless, and because of marginal diminishing utility, such a setback would carry less negative humanitarian impact than such a setback would if it occurred today.
Overly weak assumptions regarding adaptation?
The IPCC considers what the impacts of climate change will be in 2050; a full 35 years away. My intuition is that over the course of the next 35 years, human society will adapt in such a way that the issues that the IPCC describes will have a smaller negative humanitarian impact than the IPCC suggests. I have not vetted the references given by the IPCC, and may be mistaken about their implicit assumptions, so my remarks should be taken with a grain of salt.
To explicitly address some of the impacts discussed in the IPCC:
- Crop productivity and hunger in Africa — The IPCC projects that in 2050, at least 208 million people will be at risk of hunger even without climate change: only ~ 3x fewer than today. New technologies for the production of starch could make the number much smaller.
- Floods due to rising sea levels — The IPCC mentions dikes and nourishment as possible adaptive responses, but doesn’t mention the possibility that people will move away from coastal areas as sea levels rise. Individual people and families might move away to avoid flooding. On the time scale of 5 years, people are usually unwilling to move, but over the course of 35 years, it might happen organically. Over time, more cities will be built, and people will migrate to them. Cities are more likely to be built in areas that are not prone to flooding, than in areas that are.
- Significant loss of species and biodiversity — Over the next 35 years, humans may make a concerted effort to preserve rare species by collecting them and housing them in zoos. (I recognize that this would have to happen well before 35 years elapsed in order to avoid the loss.)
There are also more general relevant considerations:
- Geoengineering — It may be possible to reverse or halt climate change via geoengineering. Geoengineering carries its own risks, but its potential would seem to be positive in expectation, although the situation is murky.
- Unpredicted technologies — Technological progress is unpredictable, and it could be that we can develop technologies that mitigate effects such as droughts, even if we can’t see these technologies in advance. There are potential unpredicted technologies that would make climate change worse, such as those that facilitate cheaper extraction of fossil fuel, but on balance, technological progress usually enables humans to solve problems more than to create them.
Breakthroughs in genetic engineering, artificial intelligence and whole brain emulation could also radically alter human needs themselves.
The IPCC as overly optimistic?
Some people have voiced the concern that the IPCC is overly optimistic in its predictions of climate change impacts. This is corroborated by the recent paper Climate change prediction: Erring on the side of least drama, which reports that historic IPCC predictions of current impacts of climate change have erred on the overcautious side. But given that the IPCC represents a consensus, barring tail risk, it seems unlikely that the IPCC is overly optimistic by a huge margin.
Tail risk
The biggest reason to be concerned about climate change is that there’s a small probability that the negative impact could be huge.
There is a danger of permafrost in the Arctic melting and releasing methane, creating a feedback loop where the release of methane, global warming, and the melting of the permafrost reinforce each other. This could increase global temperature by 3.5 degrees Celcius, greatly exacerbating all other impacts of climate change. Even if this doesn’t happen, it could be that climate models are wrong, and that the amount by which the earth temperature will rise is much greater than current models predict.
The potential impacts of a much larger increase in temperature than what the IPCC predicts are less studied. One starting point for reading on this is the 4degrees and beyond international climate conference.
About the author: I worked as a research analyst at GiveWell from April 2012 to May 2013. All views expressed here are my own.
Acknowledgements: Thanks to Nick Beckstead, Vipul Naik and Carl Shulman for helpful suggestions.
To be continued: I'll be writing up a follow up report about the implications of the projected impacts for effective philanthropy.
44 comments
Comments sorted by top scores.
comment by passive_fist · 2013-05-23T07:34:12.078Z · LW(p) · GW(p)
"Significant loss of species and biodiversity — Over the next 35 years, humans may make a concerted effort to preserve rare species by collecting them and housing them in zoos. "
The extremely dangerous effects of biodiversity cannot simply be handwaved out like this.
Firstly, this is impossible since the vast majority of species are unknown to science (remember that vertebrates and confierous plants only represent a small fraction of species). Actually obtaining viable samples from the 70,000 vertebrate species, 1,000,000+ invertebrate species, 300,000+ plant species and 100,000,000+ estimated bacterial species would be a herculean task of such magnitude that no one would ever pay for it. Let alone actually obtaining a genetically diverse pool - which would require at least 500 random individuals from each species. Zoos often have to trade individuals with each other and interbreed in order to maintain a genetically viable population.
But all of this is ignoring that we already have a zoo that houses all species and is perfectly capable of supporting all of them in the foreseeable future, and doesn't cost anything to run. The only thing it asks is that we not destroy it.
Replies from: drethelin, JonahSinick↑ comment by drethelin · 2013-05-24T05:10:42.229Z · LW(p) · GW(p)
"Doesn't cost anything to run" is silly. If maintaining the ecoysystem was free, we'd do it because most people prefer there to be one rather than not. Maintaining the ecosystem trades off against all sorts of other things we want, and if we have to give them up to maintain it, that's what it costs to run.
Replies from: passive_fist↑ comment by passive_fist · 2013-05-24T21:33:03.237Z · LW(p) · GW(p)
It doesn't cost us anything in that we don't have to give up anything we currently have (provided that we execute the right policies to maintain current levels of prosperity without expanding into nature even more). You're talking about an imagined future cost, and that gets pretty tricky. Who's to say that it doesn't cost us to keep the Milky Way running, since in a billion years we could conquer it all?
↑ comment by JonahS (JonahSinick) · 2013-05-23T14:32:21.046Z · LW(p) · GW(p)
The extremely dangerous effects of biodiversity cannot simply be handwaved out like this.
Why do you say extremely dangerous? The IPCC predicts that climate change will cause the extinction of 20%-30% of species by 2100. This seems bad, but not extremely dangerous.
Firstly, this is impossible since the vast majority of species are unknown to science
I don't have subject matter knowledge, but these seems like good points.
But all of this is ignoring that we already have a zoo that houses all species and is perfectly capable of supporting all of them in the foreseeable future, and doesn't cost anything to run. The only thing it asks is that we not destroy it.
This is easier said than done. Do you have proposals?
Replies from: passive_fist↑ comment by passive_fist · 2013-05-23T20:25:25.947Z · LW(p) · GW(p)
I suppose 'extremely dangerous' is subjective, but I'm confident in my usage of the term. It has been demonstrated that relationships between species are held in an extremely delicate balance. Extinction of one species can lead to another, which can lead to the blowing-up of a population of another (because it lost a major predator), which can lead to the extinction of others.
In fact we have been observing such fluctuations in the present. We have seen many species suddenly collapse, while others blow up with devastating results (algae blooms). And this is just with a few percent biodiversity loss, let alone 30%.
But the larger point is that we simply don't know what will happen. The relationships between species are very complex. It's possible that the entire food chain that we depend on will collapse (for example, if pollinating insects went instinct). It's also possible that loss of biodiversity will have little effect on humans. We are extremely ignorant about it - but that's no excuse to continue doing it.
"This is easier said than done. Do you have proposals?"
There have been many proposals where just diverting a few percent of worldwide GDP would eliminate global warming. Among them, adoption of renewables and nuclear power.
Replies from: JonahSinick↑ comment by JonahS (JonahSinick) · 2013-05-23T22:42:03.364Z · LW(p) · GW(p)
On an object level your point seems persuasive, but my prior is still that it's not a big issue, because I haven't seen other people highlight this forcibly before. Are you familiar with some discussion of it?
There have been many proposals where just diverting a few percent of worldwide GDP would eliminate global warming. Among them, adoption of renewables and nuclear power.
I mean actionable proposals for effective altruist types. I support adoption of renewables and nuclear power, but I don't know what I or my friends can do to encourage it in a cost-effective way.
[Edit: I'd add that I think that what you describe falls under the category of "tail risk." I haven't heard this issue discussed, and It would be great if you were to write up a detailed account of your view, with citations.]
Replies from: passive_fist, Yosarian2↑ comment by passive_fist · 2013-05-24T21:43:25.416Z · LW(p) · GW(p)
Loss of biodiversity has definitely been highlighted frequently, although it is often done without reference to climate change (even though it is acknowledged to be the most important factor in general), because people want to have their opinions heard without getting mired in political debates. But the material is there and can be revealed with a simple google search. I'm hesitant to give you links myself because I'd feel like I'm just cherry-picking the articles I want you to read.
I don't know what I or my friends can do to encourage it in a cost-effective way.
I don't either, aside from the usual cliche of 'spreading awareness' .
↑ comment by Yosarian2 · 2013-05-31T09:36:40.640Z · LW(p) · GW(p)
There has been a lot of concern about loss of biodiversity and the possible chain effects of collapse to one part of the food chain or another.
It also seems likely that the effects of global warming will be magnified by other effect.s For example, naturally speaking, if the Earth's climate change many animals would normally just migrate north and be fine, but we've broken up huge wilderness areas into many small pieces of "wildlife preserve", often relatively small areas of natural environment surrounded by built-up areas of human habitation.
A lot of scientists have described what is going on now as a mass extinction event, on a scale that's only happened 5 times previously in Earth's history.
As for your other question:
I mean actionable proposals for effective altruist types. I support adoption of renewables and nuclear power, but I don't know what I or my friends can do to encourage it in a cost-effective way.
Well, if you're interested, there are a number of fairly simple things people can can do to reduce their power consumption and the amount of fuel they use in transportation by a few percent. This has other positive effects as well, like reducing air pollution. Not that conservation efforts are going to solve the problem by themselves, but at least they may buy us a little time.
comment by knb · 2013-05-22T23:46:40.202Z · LW(p) · GW(p)
LW poster Tim Tyler wrote an interesting contrarian article on his website about global warming. I'm not really endorsing the main argument, but it had a lot of information I was unfamiliar with before reading.
Replies from: Desrtopa, Lukas_Gloor, timtyler↑ comment by Desrtopa · 2013-05-23T03:23:36.982Z · LW(p) · GW(p)
I had a fairly long running argument with him about this some years back, suffice to say that none of the information he presents is little known among climate scientists, and they don't share his optimism. The "danger" of reglaciation is completely overblown (we've most likely already broken the ice age cycle, having boosted atmospheric CO2 back up to Pleistocene levels,) and even if we did enter a new glaciation period, it would be such a slow process as to pose relatively little danger to our society.
He's operating under a largely naive "warmer is better" model which fails to account for the difficulty ecological systems have in adapting to rapid changes.
Replies from: knb, timtyler, timtyler↑ comment by knb · 2013-05-23T07:04:36.692Z · LW(p) · GW(p)
suffice to say that none of the information he presents is little known among climate scientists
I was never under the impression that climate scientists didn't know these things. However I'd been reading editorials and popular science articles about climate change for years before I read Tyler's post and still didn't know a lot of the really basic facts Tyler presented. For example, I did not understand the distinction between interglacials and ice ages, or the fact that Earth has usually had zero polar ice throughout its history.
From the pop science articles and editorials I'd been reading, I was really badly informed about the topic--and these are the ways almost everyone learns about climate change issues. Since then I've talked to a many people about this, and most people have known very few of these facts.
He's operating under a largely naive "warmer is better" model which fails to account for the difficulty ecological systems have in adapting to rapid changes.
If you believe rapid changes are bad, that actually is evidence that warmer is better, because warm earth eras are dramatically more stable. Ice ages have dramatic positive feedback cycles, where cooling triggers further cooling and warming triggers further warming. Because of this, there have been repeated "snowball earth" events in which life was driven to near extinction. Regardless of what humans do, these cycles will continue until the ice age ends.
The "danger" of reglaciation is completely overblown (we've most likely already broken the ice age cycle, having boosted atmospheric CO2 back up to Pleistocene levels,) and even if we did enter a new glaciation period, it would be such a slow process as to pose relatively little danger to our society.
I agree with you here. Climate change takes centuries or millennia to produce dramatic changes. That just doesn't seem terribly important in light of exponential economic and technological change that produces dramatic effects orders of magnitude faster.
Replies from: Desrtopa↑ comment by Desrtopa · 2013-05-23T13:53:27.158Z · LW(p) · GW(p)
f you believe rapid changes are bad, that actually is evidence that warmer is better, because warm earth eras are dramatically more stable. Ice ages have dramatic positive feedback cycles, where cooling triggers further cooling and warming triggers further warming.
The warming event we're triggering is itself a much more rapid change than the warming and cooling events which occur during an ice age. Going back to Pleistocene level stability might have advantages in the long run, but a rapid shift to Pleistocene level climate is itself going to be harmful.
I agree with you here. Climate change takes centuries or millennia to produce dramatic changes. That just doesn't seem terribly important in light of exponential economic and technological change that produces dramatic effects orders of magnitude faster.
The largest effects aren't going to show up for centuries or more, but at the present rate, we're looking at quite a large ecological impact within this century.
I certainly wouldn't call climate change the top risk to humanity, or even close to it, but a mass extinction event is going to be a significant quality-of-life issue, even if we're not one of the species lost.
↑ comment by timtyler · 2013-05-31T10:56:09.362Z · LW(p) · GW(p)
The "danger" of reglaciation is completely overblown (we've most likely already broken the ice age cycle, having boosted atmospheric CO2 back up to Pleistocene levels,)
Go, anthropocentric warming! Fingers crossed on that one, though - at least until there's a consensus on what causes the glacial cycles and their periodic shifts.
and even if we did enter a new glaciation period, it would be such a slow process as to pose relatively little danger to our society.
All climate change is slow - and not-very threatening to civilization.
The "danger" of reglaciation is completely overblown (we've most likely already broken the ice age cycle, having boosted atmospheric CO2 back up to Pleistocene levels,)
Go, anthropocentric warming! Fingers crossed on that one, though - at least until there's a consensus on what causes the glacial cycles and their periodic shifts.
and even if we did enter a new glaciation period, it would be such a slow process as to pose relatively little danger to our society.
All climate change is slow - and not-very threatening to civilization.
↑ comment by timtyler · 2013-05-31T10:17:41.283Z · LW(p) · GW(p)
The "danger" of reglaciation is completely overblown (we've most likely already broken the ice age cycle, having boosted atmospheric CO2 back up to Pleistocene levels,)
Go, anthropocentric warming! Fingers crossed on that one, though - at least until there's a consensus on what causes the glacial cycles and their periodic shifts.
and even if we did enter a new glaciation period, it would be such a slow process as to pose relatively little danger to our society.
All climate change is slow - and not-very threatening to civilization.
none of the information he presents is little known among climate scientists, and they don't share his optimism.
Follow the money. They are funded when they project doom. Thus the IPCC fiasco.
He's operating under a largely naive "warmer is better" model which fails to account for the difficulty ecological systems have in adapting to rapid changes.
Warmer is better - when you're in an ice age. I acknowledge rapid change will cause some problems. However, these are overblown by the media, while the large benefits go largely ignored. It seems like pure doom-bias to me. Eco-apocalypse sells, while "actually, thiings might get better in most places" does not.
↑ comment by Lukas_Gloor · 2013-05-23T00:48:27.735Z · LW(p) · GW(p)
And here a reason why reglaciation might be a good thing.
Replies from: timtyler↑ comment by timtyler · 2013-05-23T01:23:04.230Z · LW(p) · GW(p)
That looks like deathophilia :-(
Replies from: Lukas_Gloor, knb↑ comment by Lukas_Gloor · 2013-05-23T20:21:20.568Z · LW(p) · GW(p)
Even if people think there is enormous value in living long and happy lives, it is still coherent to acknowledge that there might be existences that are not worth living. The facts seem to point towards this being the case for the vast majority of wild animals. I'm just pointing out the obvious conclusion.
↑ comment by knb · 2013-05-24T02:48:30.804Z · LW(p) · GW(p)
Appropriate, since ice-nine is a chemical in Kurt Vonnegut's novel Cat's Cradle which causes all water to freeze, exterminating all life on earth.
Replies from: Lukas_Gloor↑ comment by Lukas_Gloor · 2013-05-24T23:23:50.184Z · LW(p) · GW(p)
If your utility function includes stuff you want to minimize, then you cannot a priori rule out that freezing the world may be the best outcome, as this would depend on empirical circumstances. It seems weird to me why anyone would reject a value judgement based on a conclusion that is a possibility for all value systems (or at least the ones that contain minimization); this would be getting it backwards, I think.
Also note that my initial comment was about reglaciation, which doesn't necessarily imply the extinction of all life on earth. All else being equal, wouldn't it be better to reduce the amount of wild animals, if it is empirically the case that the vast majority of wild animals die shortly after birth in ways that are presumably painful? If your answer is "That looks like deathophilia", then I'm somewhat lost to be honest.
Finally, depending one one's view, there is a relevant difference between death an non-existence. One could think that one poses a problem whereas the other doesn't.
Replies from: knb↑ comment by knb · 2013-05-25T02:02:22.351Z · LW(p) · GW(p)
Even if you think animal suffering is bad enough that it would be a good idea to kill them all, reglaciation is just a bizarre way of achieving this. First of all it doesn't actually kill off all animals. Also it would be an amazingly slow and destructive and expensive and... stupid way of killing things.
Replies from: Lukas_Gloor↑ comment by Lukas_Gloor · 2013-05-25T15:25:19.966Z · LW(p) · GW(p)
I wasn't commenting on practical strategies about reducing the number of wild animals. All I was saying is that there are positive consequences of reglaciation and that they might outweigh the negative consequences. Of course, there are probably ways to bring about the positive consequences faster and more effectively while still preventing the negative ones. (Don't interpret too much into my account name here, I didn't even realize how fitting it was to this discussion until you pointed it out.)
Replies from: knb↑ comment by timtyler · 2013-05-23T00:43:22.487Z · LW(p) · GW(p)
I notice that the great Matt Ridley puts out a stream of broadly-similar material on his blog these days.
For example, his latest post is subtitled: "Global warming will probably be a net benefit for several decades".
I write little about climate - simply because it is a relatively insignificant issue. It's main significance seems to be due to all the time which is wasted on it - time which could be being put to much better use.
comment by OrphanWilde · 2013-05-22T12:47:22.787Z · LW(p) · GW(p)
Did you deliberately avoid listing potential benefits because you were worried your article already came across as too positive?
Replies from: JonahSinick↑ comment by JonahS (JonahSinick) · 2013-05-22T15:42:10.615Z · LW(p) · GW(p)
The IPCC already discusses some potential benefits: for example, there's discussion increased water runoff reducing water stress in some parts of the world. My post is intended only as very high level summary, so I didn't do research on potential benefits that are not discussed in the IPCC, but if there are some that seem especially important to you, I'll consider adding them.
Replies from: pcm↑ comment by pcm · 2013-05-23T19:14:03.322Z · LW(p) · GW(p)
This somewhat controversial paper estimates a net 849252 fewer deaths in 2050 due to warming from 6 disease types that they studied.
comment by buybuydandavis · 2013-05-23T09:46:58.858Z · LW(p) · GW(p)
Last I heard, the increased carbon dioxide was increasing temperature mainly in colder region, increasing crop yields, increasing rain, greening the planet, and had likely pushed back the end of the current inter glacial by tens of thousands of years. The estimated sensitivity to a doubling of atmospheric carbon dioxide has come down, and global temperatures have been essentially flat for a decade.
Replies from: JonahSinick↑ comment by JonahS (JonahSinick) · 2013-05-23T14:15:52.758Z · LW(p) · GW(p)
Can you give a reference?
Replies from: buybuydandavis↑ comment by buybuydandavis · 2013-05-25T20:48:44.935Z · LW(p) · GW(p)
Climate sensitivity.
http://reason.com/blog/2013/05/21/future-global-warming-likely-less-second
http://reason.com/blog/2013/04/26/climate-sensitivity-trending-down-is-a-c
Flat for a decade
http://www.drroyspencer.com/latest-global-temperatures/
Desrtopa, at least, agrees with reglaciation being pushed back:
http://lesswrong.com/lw/hi1/potential_impacts_of_climate_change/918k
Couldn't find the others. They were older articles I'd read.
Replies from: arundelo↑ comment by arundelo · 2013-05-25T21:02:26.849Z · LW(p) · GW(p)
s/Desrtopia/Desrtopa/
Replies from: buybuydandavis↑ comment by buybuydandavis · 2013-05-26T02:00:43.135Z · LW(p) · GW(p)
Oops. Thanks.
comment by Thomas · 2013-05-22T13:16:43.434Z · LW(p) · GW(p)
Now, when we have nearly doubled the amount of CO2 in the atmosphere in the last decades, in dry places like Death Valley or Riyadh or Siberia, the effect of CO2 should be quite visible.
Morning in dry desserts should be warmer due to the CO2, relatively more dominant GHG there where the water vapor is tiny.
But are they? All temperature records are AFAIK quite old, No no such data to be found with Google. Mornings in Riyadh as they used to be.
Replies from: fubarobfusco, Manfred↑ comment by fubarobfusco · 2013-05-22T14:13:42.423Z · LW(p) · GW(p)
Now, when we have nearly doubled the amount of CO2 in the atmosphere in the last decades, in dry places like Death Valley or Riyadh or Siberia, the effect of CO2 should be quite visible.
http://weather-warehouse.com/WeatherHistory/PastWeatherData_DeathValley_DeathValley_CA_April.html
Maximum temperatures in Death Valley have indeed been trending up over the last decades. The yearly maxima in the last ten years range from 100 to 113F, mean 106.7F; the maxima in the '60s ranged from 89 to 106F, mean 100.8 — an increase of ~6 degrees F. Mean low, mean high, and mean temperatures are up about ~2 degrees.
So, that checks out.
http://www.tutiempo.net/en/Climate/Riyadh/404380.htm
Looks like they're up a bit in Riyadh, too, although that's just from eyeballing it.
So, you're right — the effects do appear to be quite visible.
Replies from: OrphanWilde, None↑ comment by OrphanWilde · 2013-05-22T17:18:22.355Z · LW(p) · GW(p)
You're confusing climate and weather. Average temperatures have remained about the same, average maximum temperatures have remained about the same, average minimum temperatures have remained about the same. The absolute lowest temperature recorded was recorded in 99.
Incidentally, CO2 should show the strongest effects on daily minimums, not daily maximums, owing to the mechanisms of its forcing. (Something which turns up in temperature records throughout the rest of the nation, incidentally.)
Replies from: fubarobfusco, gjm↑ comment by fubarobfusco · 2013-05-22T19:48:45.685Z · LW(p) · GW(p)
Your criticism would be correct if addressed to Thomas's post. The argument there was of the form "If X, then Y" ... with the implication of not-Y and therefore not-X. My post was just establishing that Y.
Replies from: OrphanWilde↑ comment by OrphanWilde · 2013-05-22T20:02:17.078Z · LW(p) · GW(p)
Your post is establishing Z, actually, a largely unrelated temperature phenomenon - maximum temperature. Hence my second paragraph.
Replies from: JoshuaZ↑ comment by JoshuaZ · 2013-05-23T02:52:24.891Z · LW(p) · GW(p)
Average temperature is relevant in this context, as average temp goes up we should expect the maximum to go up as well.
Replies from: OrphanWilde↑ comment by OrphanWilde · 2013-05-24T13:25:16.892Z · LW(p) · GW(p)
Not necessarily. Can't find the paper now, but a team which analyzed nationwide temperature measurement stations found that stations with good placement (that is, not placed right next to an air conditioning unit, or next to a runway, or somewhere else where external heat sources messed with the measurements) experienced considerably increases in daily minimums, but only minute differences in daily maximums; a trend which produces a higher average relative to the maximum than might be expected.
↑ comment by gjm · 2013-05-22T22:42:13.558Z · LW(p) · GW(p)
Typical estimates of current global warming rate are on the order of 0.015 K per year.
Least-squares fitting of a straight line to the monthly average temperatures in Death Valley from the site above, after subtracting off month-by-month averages to avoid getting confused by ordinary seasonal variation, gives a rate of increase of 0.027 degrees F per year, or ... 0.015 K per year.
So it looks to me as if the Death Valley figures fit perfectly with the consensus view of global warming. In particular, it is not true that "average temperatures have remained about the same" unless you count the current consensus view of global warming as saying that global average temperatures have remained about the same.
Similar fits for the other statistics in that table, in order of appearance there, all in K/year: monthly lowest temp +0.010, monthly highest temp +0.044, monthly highest daily min temp -0.020 (!), monthly lowest daily max temp +0.018, monthly avg daily min temp +0.0004, monthly avg daily max temp +0.029.
Could you say more in support of your claim that CO2 should show its strongest effect on daily minima rather than maxima? I had a quick look with Google and all I found was some anti-AGW website saying that increases in daily minima are not an indication of global warming because they're all to do with urban heat islands.
(Fair enough if the answer is that you don't feel like paying the karma tax for replying to something downstream of a severely downvoted comment.)
Replies from: OrphanWilde↑ comment by OrphanWilde · 2013-05-24T13:22:33.014Z · LW(p) · GW(p)
The number of data points in that sample, at least, probably don't support that degree of precision.
As for the minima versus maxima claim, I can only point you in the right direction; Google "declining DTR".
Unfortunately the science is a lot more all-over-the-place than I had anticipated; the NOAA appears to agree, more or less, with the skeptical claim there (see http://www.nws.noaa.gov/ost/climate/STIP/FY11CTBSeminars/lzhou_052511.htm ), whereas the IPCC appears to disagree (see http://www.ipcc.ch/ipccreports/tar/wg2/index.php?idp=422 ) . Then you have people making claims at odds with both of them (see http://www.co2science.org/articles/V3/N33/C3.php )
Unfortunately it appears the field has undergone a lot of changes in the past five years. When I last researched the matter, it was considered good evidence -for- AGW (albeit evidence for a "lukewarmist" position), and attention had just been focused to it by the products of a skeptical initiative to document the conditions of temperature stations and a subsequent paper which attempted to de-bias the UHI effect out of the temperature record - given that the de-bias attempt is what -produced- the attention on daily minima (which it found to have increased substantially, with only a statistically insignificant increase in daily maxima), I'm slightly suspicious of any claim that an increase in daily minima has to do with the UHI effect. (Namely, correcting for the UHI -produces- a stronger trend in daily minima compared to daily maxima or averages; if the UHI were -responsible- for this trend, we'd expect the reverse.)
But I have no idea what happened to the original papers, which were substantially better than what I can find today.
↑ comment by [deleted] · 2013-05-22T14:41:44.895Z · LW(p) · GW(p)
Arctic amplification (the shifting of the arctic ocean out of a stable state with lots of ice year round to another one with no summer ice and diminishing winter ice due to positive feedbacks in albedo and airflow) means that it's much more visible near the North pole than in any of the temperate zones at this time. In recent years it's been several degrees C higher than the first half of the 20th century average and it is possible there will be no summer ice (barring some that gets pushed up against the North coast of Greenland) by the 2020s. That's quite a visible effect as well, especially because the diminishing temperature difference from the polar air mass to the subtropical air masses causes the jet stream to slow down and become more convoluted (its basically a heat engine) and cause warm and cool air masses to move West to East over the temperate zones slower, increasing weather variability.
comment by Lumifer · 2013-05-22T14:36:06.743Z · LW(p) · GW(p)
People, update your data! The temperature for the last 15 years is basically flat. Real-world measurements are dropping below the IPCC models' forecasts. The hysterics from 10 years ago look much overstated today.
And as to consequences, look carefully at the Stern report (2007). First, until about +2 degrees warming, the net effect is positive. Second, the report was forced to cheat by assuming a very low discount rate in order to make the far-off effects significant enough to justify any changes today.
Replies from: None↑ comment by [deleted] · 2013-05-22T17:44:47.735Z · LW(p) · GW(p)
The low rate of average air temperature increase is probably partially due to a confluence of various oscillations that move heat energy back and forth between the hydrosphere and atmosphere, along with the recent increase in industrial aerosols from China (which they very much want to get rid of so that their people can, yknow, breathe). Most of the thermal energy goes into the water at any given time but it can easily come out again. http://www.youtube.com/watch?v=u_0JZRIHFtk is a quick and dirty visualization of this effect.
The recent arctic ice breakdown is far more rapid than any models predicted.
I have no reason to think that climates changing will end civilization or directly kill billions of people. What it will do is stress many ecologies to near the breaking point for a few centuries, make temperate zone weather more inconsistent and unpredictable, and require all sorts of adaptation efforts as the climate bands that our current agricultural and urban systems have sprung up around change.